java 位向量

Posted 2020-10-26 java渣渣

public class BitVectory {
    private int count;
    private int[] a;
    private static final int BIT_LEN = 32;
    private static final int MASK = 0x1f; //16禁止表示 10进制31
    private static final int SHIFT = 5;

    public BitVectory(int count) {
        this.count = count;
        init(count);
    }

    private void init(int count) {
        a = new int[(count - 1) / BIT_LEN + 1];
        for (int i = 0; i < count; i++) {
            clear(i);
        }
    }

    private void clear(int i) {
        a[i >> SHIFT] &= ~ (1 << (i & MASK));
    }

    //
    public void set(int i) {
        a[i >> SHIFT] |= (1 << (i & MASK));
    }

    public List<Integer> getSortedArray() {
        List<Integer> list = new ArrayList<>();
        StringBuilder s = new StringBuilder();
        for (int i = 0; i < count; i++) {
            s.append(get(i));
            if (get(i) == 1) {
                list.add(i);
            }
        }
        System.out.println(s.toString());
        return list;
    }

    private int get(int i) {
        return Integer.bitCount(a[i >> SHIFT] & (1 << (i & MASK)));
    }


    public static void main(String[] args) {
        BitVectory bitVectory = new BitVectory(38);

        List<Integer> list = new ArrayList<>(38);
        for (int i = 0; i < 38; i++) {
            list.add((int) (Math.random() * 36));
        }

        list.forEach(e -> {
            bitVectory.set(e);
        });

        List<Integer> sortedArray = bitVectory.getSortedArray();
        System.out.println(sortedArray.size() + "\t" + sortedArray);
        System.out.println(Integer.toBinaryString(bitVectory.a[0]));
        System.out.println(bitVectory.a.length);
        System.out.println(Arrays.toString(bitVectory.a));
    }

}

利用位向量对 0-N的数据进行排序 N / mask + 1个数组a来表示这些数